The invention relates to an automatic testing apparatus for testing the circular spacing of gears, in which during the testing operation the gear is caused to rotate continuously in one direction by its own power source, and a slide on the frame of the apparatus is displaceable by a drive mechanism substantially radially toward the gear and back away from it for performing the individual testing operations. The slide has two measuring feelers supported pivotably on it, which are movable along with the gear counter to spring force and which cooperate with preferably inductive transducers. The measuring feelers each point toward the same flank (right or left) of two adjacent teeth in the vicinity of the pitch circle of the gear. Means are provided for applying the measuring feelers, under spring force, to the tooth flanks after the feelers have been driven into the tooth gaps and for moving them away from the tooth flanks, counter to spring force, after the testing operation has been performed. The first measuring feeler is embodied as a reference feeler and is connected with switching means by which, at a predetermined pivoted position of this feeler, the pickup or emission of a measurement value from the second feeler is brought about on the one hand and by which on the other hand the retraction of the measuring feelers out of the teeth and their re-insertion, retarded in an adjustable manner, into the teeth are controllable by means of the appropriate switching of the slide drive. The invention furthermore relates to a method for testing the circular spacing of continuously rotating gears and, in a further development, to a method for measuring deviations in gear concentricity, in tooth thickness and in tooth gaps for continuously rotating gears.
The known testing apparatuses for circular spacing, which permit relative testing by means of a comparison of sequentially ascertained measurement values, are suitable both for large gears to be tested directly on the gear cutting machine and for small gears which are tested on a measuring machine, to which end such testing apparatuses are usually transportable. The testing is effected dynamically because of the continuously rotating gear.
The two measuring feelers mentioned above are located on a slide, by means of which they can be inserted into the gear teeth against a fixed stop and then retracted once again after the measurement operation has been performed. For the testing operation per se, the measuring feelers are positioned approximately with respect to the pitch circle diameter, being placed precisely on a common circular path; in practice, this is accomplished by making the measuring feeler just touch one flank of the gear tooth. The feelers are also positioned such that for the measuring operation they rest first on the left-hand tooth flanks, for instance, and when the feelers first engage these flanks, the transducers of these feelers are balanced at zero.
For a test object which rotates continuously, the measuring feelers are inserted one after another into sequential tooth gaps. After contacting the respective tooth flanks, the feelers follow the test object for a certain distance, until the reference feeler again attains the value of zero. This causes the measurement value transfer, or the emission of the value corresponding to the deviation in spacing, at the transducer of the second feeler and also causes the retraction of the feelers from the teeth which then occurs. The automatic control of this insertion and retraction of the feelers from the teeth is known and will accordingly not be described in detail here.
Once the gear has made one revolution, so that the feelers have come into contact with all the left flanks of the teeth, then the measuring feelers are again placed on a common circular path against the right tooth flanks of adjacent teeth, and the transducers connected with the feelers are again set to zero. The spacing is then tested via the right flanks, with the gear now revolving in the opposite direction.
To prevent the measuring feelers from scraping the tooth flanks or colliding with the teeth during their insertion into and retraction out of the teeth, it is conventionally provided that for shifting them from one tooth gap to the next, the feelers are raised by switching means from the flanks which they have scanned or which they are about to scan.
The known testing unit has the disadvantage that two complete gear revolutions are required to detect spacing deviations at the left and right tooth flanks, and between the two revolutions the measuring feelers also have to be changed over from one tooth flank to the other. This means that a great deal of time and expense must be expended, a situation which in testing on the gear machine itself is further increased quite substantially because a gear cutting machine with a very high hourly output cannot then be used for production during the testing operation.
In order to measure the deviations in gear concentricity, tooth thickness and tooth gaps--which become of interest if the gear is found acceptable in terms of spacing--a further testing unit is also required. In order to measure deviations in tooth gaps and gear concentricity, a ball-like measuring feeler is inserted into each tooth gap of the continuously revolving test object, and the depth of insertion in each case is measured; this permits a conclusion to be made as to whether there are deviations from one tooth gap to another, and in the final analysis it permits the deviation in concentricity to be ascertained. For the deviations in tooth thickness, one forked measuring feeler after another is placed against each tooth of the gear, and here again the insertion depth, or the deviation in the insertion depth from an initially adjusted zero setting, is ascertained. Thus at least one further revolution of the gear, and a separate testing unit, are required to make these last three measurements, which still further increases the time and expense required for gear testing.